Optimization and physicochemical characterization of a triamcinolone acetonide-loaded NLC for ocular antiangiogenic applications

Preparation, characterization and biocompatibility studies of thermoresponsive eyedrops based on the combination of nanostructured lipid carriers (NLC) and the polymer Pluronic F-127 for controlled delivery of ibuprofen

CONTEXT

Nanostructured lipid carrier (NLC) dispersions present low viscosity and poor mucoadhesive properties, which reduce the pre-corneal residence time and consequently, the bioavailability of ocular drugs.

OBJECTIVE

The aim of this study was to prepare thermoresponsive eyedrops based on the combination of lipid nanoparticles and a thermoresponsive polymer with mucomimetic properties (Pluronic® F-127).

MATERIALS AND METHODS

NLC_i dispersions were prepared based on the melt-emulsification and ultrasonication technique. Physicochemical and morphological characteristics of the colloidal dispersions were evaluated. The formulation was also investigated for potential cytotoxicity in Y-79 human retinoblastoma cells and the in vitro drug release profile of the ibuprofen was determined.

RESULTS

NLC_i showed a Z-average below 200 nm, a highly positive zeta potential and an efficiency of encapsulation (EE) of ∼90%. The gelification of the NLC_i dispersion with 15% (w/w) Pluronic® F-127 did not cause significant changes to the physicochemical properties. The potential NLC-induced cytotoxicity was evaluated by the Alamar Blue reduction assay in Y-79 cells, and no relevant cytotoxicity was observed after exposure to 0-100 µg/mL NLC for up to 72 hours. The optimized formulations showed a sustained release of ibuprofen over several hours.

DISCUSSION AND CONCLUSION

The strategy proposed in this work can be successfully used to increase the bioavailability and the therapeutic efficacy of conventional eyedrops.

Ophthalmic applications of lipid-based drug nanocarriers: an update of research and patenting activity

Ophthalmic diseases collect great attention by researchers and pharmaceutical technologists, since they can dramatically worsen the quality of life. Because of the limited duration of action on the eye surface, and anatomical/physiological barriers to drug penetration from it into the inner eye structures, conventional ocular formulations are generally unable to perform at their best. Nanotechnology approaches can represent a solution to improve the therapeutic efficiency, compliance and safety of ocular drugs. In this respect, lipid-based nanocarriers are among the most interesting systems. Their composition and production methods make them highly biocompatible and safe formulations. This review illustrates the developments achieved in ocular drug delivery using lipid-based nanocarriers, with a critical revision of recent scientific articles and filed patents.

Modified NLC-loaded coumarin for pharmaceutical applications: the improvement of physical stability and controlled release profile

BACKGROUND

Coumarin-6 is a lipophilic dye and is often used as a model in delivery system.

OBJECTIVE

The aim of this study was to improve the nonstructured lipid carrier (NLC) system loading with lipophilic molecule, coumarin-6, and to investigate its characteristics in terms of physical stability and controlled release profile.

MATERIALS AND METHODS

Initially, the selection of the coating polymer was observed. Then, the preparation of the conventional NLC-loaded coumarin-6 was compared to the modified NLC-loaded coumarin-6 via the probe sonication. The physical properties and stability were determined by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques. The release profile was established using fluorescent spectroscopic method.

RESULTS AND DISCUSSION

The size and zeta potential measurement showed significant decrease in the size range of the modified NLC-loaded coumarin and the lower intensity of the surface charge compared to the NLC-loaded coumarin. The change of crystallinity observed from DSC and XRD techniques indicated the molecular dispersion of coumarin-6 in the lipid matrix of NLC. The FT-IR spectra were also proven that coumarin-6 was entrapped in the NLC molecule. The result showed comparable controlled release profile to the conventional preparation with no difference on the cytotoxicity level.

CONCLUSIONS

The modified NLC delivery system, therefore, exhibited the acceptable potential as a nanocarrier.

Solid Lipid Nanoparticles and Nanostructured Lipid Carriers: Structure, Preparation and Application

Lipid nanoparticles (LNPs) have attracted special interest during last few decades. Solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs) are two major types of Lipid-based nanoparticles. SLNs were developed to overcome the limitations of other colloidal carriers, such as emulsions, liposomes and polymeric nanoparticles because they have advantages like good release profile and targeted drug delivery with excellent physical stability. In the next generation of the lipid nanoparticle, NLCs are modified SLNs which improve the stability and capacity loading. Three structural models of NLCs have been proposed. These LNPs have potential applications in drug delivery field, research, cosmetics, clinical medicine, etc. This article focuses on features, structure and innovation of LNPs and presents a wide discussion about preparation methods, advantages, disadvantages and applications of LNPs by focusing on SLNs and NLCs.

Current nanotechnology approaches for the treatment and management of diabetic retinopathy

Diabetic retinopathy (DR) is a consequence of diabetes mellitus at the ocular level, leading to vision loss, and contributing to the decrease of patient's life quality. The biochemical and anatomic abnormalities that occur in DR are discussed in this review to better understand and manage the development of new therapeutic strategies. The use of new drug delivery systems based on nanoparticles (e.g. liposomes, dendrimers, cationic nanoemulsions, lipid and polymeric nanoparticles) is discussed along with the current traditional treatments, pointing out the advantages of the proposed nanomedicines to target this ocular disease. Despite the multifactorial nature of DR, which is not entirely understood, some strategies based on nanoparticles are being exploited for a more efficient drug delivery to the posterior segment of the eye. On the other hand, the use of some nanoparticles also seems to contribute to the development of DR symptoms (e.g. retinal neovascularization), which are also discussed in light of an efficient management of this ocular chronic disease.

Follicular delivery of spironolactone via nanostructured lipid carriers for management of alopecia

Spironolactone (SL) is a US Food and Drug Administration-approved drug for the treatment of hypertension and various edematous conditions. SL has gained a lot of attention for treating androgenic alopecia due to its potent antiandrogenic properties. Recently, there has been growing interest for follicular targeting of drug molecules for treatment of hair and scalp disorders using nanocolloidal lipid-based delivery systems to minimize unnecessary systemic side effects associated with oral drug administration. Accordingly, the objective of this study is to improve SL efficiency and safety in treating alopecia through the preparation of colloidal nanostructured lipid carriers (NLCs) for follicular drug delivery. SL-loaded NLCs were prepared by an emulsion solvent diffusion and evaporation method using 23 full factorial design. All of the prepared formulations were spherical in shape with nanometric size range (215.6–834.3 nm) and entrapment efficiency >74%. Differential scanning calorimetry thermograms and X-ray diffractograms revealed that SL exists in amorphous form within the NLC matrices. The drug release behavior from the NLCs displayed an initial burst release phase followed by sustained release of SL. Confocal laser scanning microscopy confirmed the potential of delivering the fluorolabeled NLCs within the follicles, suggesting the possibility of using SL-loaded NLCs for localized delivery of SL into the scalp hair follicles.

A novel nanoscale-dispersed eye ointment for the treatment of dry eye disease

A novel nanoscale-dispersed eye ointment (NDEO) for the treatment of severe evaporative dry eye has been successfully developed. The excipients used as semisolid lipids were petrolatum and lanolin, as used in conventional eye ointment, which were coupled with medium-chain triglycerides (MCT) as a liquid lipid; both phases were then dispersed in polyvinyl pyrrolidone solution to form a nanodispersion. Single-factor experiments were conducted to optimize the formulations. A transmission electron micrograph showed that the ointment matrix was entrapped in the nanoemulsion of MCT, with a mean particle size of about 100 nm. The optimized formulation of NDEO was stable when stored for six months at 4 °C, and demonstrated no cytotoxicity to human corneal epithelial cells when compared with commercial polymer-based artificial tears (Tears Natural Forte). The therapeutic effects of NDEO were evaluated on a mouse model with 'dry eye'. Both the tear break-up time and fluorescein staining demonstrated therapeutic improvement, displaying a trend of positive correlation with higher concentrations of ointment matrix in the NDEO formulations compared to a marketed product. Histological evaluation demonstrated that the NDEO restored the normal corneal and conjunctival morphology and is safe for ophthalmic application.

Preparation and optimization of triptolide-loaded solid lipid nanoparticles for oral delivery with reduced gastric irritation

Triptolide (TP) often causes adverse reactions in the gastrointestinal tract when it is administered orally. This study aimed to prepare and optimize triptolide-loaded solid lipid nanoparticles (TP-SLN) with reduced gastric irritation. The microemulsion technique was used to formulate TP-SLN employing a five-level central composite design (CCD) that was developed for exploring the optimum levels of three independent variables on particle size, encapsulation efficiency (EE) and drug loading (DL). Quadratic polynomial models were generated to predict and evaluate the three independent variables with respect to the three responses. The optimized TP-SLN was predicted to comprise fraction of lipid of 49.73%, surfactant to co-surfactant ratio of 3.25, and lipid to drug ratio of 55.27, which showed particle size of 179.8 ± 5.7 nm, EE of 56.5 ± 0.18% and DL of 1.02 ± 0.003% that were in good agreement with predicted values. In addition, the optimized nanoparticles manifested a sustained-release pattern in vitro and were stable during 3 h of incubation in simulated gastric fluids without significant size change and the majority (91%) of the drug was protected. Furthermore, the nanoparticles did not show obvious gastric irritation caused by oral administration of TP in rats.

Solid Lipid Nanoparticles (SLN) and Nanostructured Lipid Carriers (NLC) for pulmonary application: a review of the state of the art

Drug delivery by inhalation is a noninvasive means of administration that has following advantages for local treatment for airway diseases: reaching the epithelium directly, circumventing first pass metabolism and avoiding systemic toxicity. Moreover, from the physiological point of view, the lung provides advantages for systemic delivery of drugs including its large surface area, a thin alveolar epithelium and extensive vasculature which allow rapid and effective drug absorption. Therefore, pulmonary application is considered frequently for both, the local and the systemic delivery of drugs. Lipid nanoparticles - Solid Lipid Nanoparticles and Nanostructured Lipid Carriers - are nanosized carrier systems in which solid particles consisting of a lipid matrix are stabilized by surfactants in an aqueous phase. Advantages of lipid nanoparticles for the pulmonary application are the possibility of a deep lung deposition as they can be incorporated into respirables carriers due to their small size, prolonged release and low toxicity. This paper will give an overview of the existing literature about lipid nanoparticles for pulmonary application. Moreover, it will provide the reader with some background information for pulmonary drug delivery, i.e., anatomy and physiology of the respiratory system, formulation requirements, application forms, clearance from the lung, pharmacological benefits and nanotoxicity.

Preparation and characterization of lipid based nanosystems for topical delivery of quercetin

The main objective of this study was to evaluate the potential of lipid nanosystems for topical delivery of the naturally occurring flavonoid quercetin. These lipid based nanosystems were manufactured using a solvent free probe ultrasonication process. Formulation factors such as the nature of the lipid (solid/combination of solid and liquid) in solid lipid nanoparticle (SLN) and nanostructured lipid carrier (NLC) systems and drug loading were evaluated to produce an optimum formulation with adequate physical stability for up to 14 weeks at 2-8°C. The mean particle size of the optimized formulation was around 282 nm, with a zeta potential value of -36.57 ± 2.67 mV, indicating the formation of a stable system. Release studies showed a biphasic release profile, characterized by an initial burst release followed by a more controlled release pattern from both SLN and NLC systems. The NLC system showed the highest improvement in topical delivery of quercetin manifested by the amount of quercetin retained in full thickness human skin, compared to a control formulation with similar composition and particle size in the micrometer range. This study demonstrated the feasibility of nanostructured lipid carrier systems for improved topical delivery of quercetin.

Scale up, optimization and stability analysis of Curcumin C3 complex-loaded nanoparticles for cancer therapy

Background

Nanoparticle based delivery of anticancer drugs have been widely investigated. However, a very important process for Research & Development in any pharmaceutical industry is scaling nanoparticle formulation techniques so as to produce large batches for preclinical and clinical trials. This process is not only critical but also difficult as it involves various formulation parameters to be modulated all in the same process.

Methods

In our present study, we formulated curcumin loaded poly (lactic acid-co-glycolic acid) nanoparticles (PLGA-CURC). This improved the bioavailability of curcumin, a potent natural anticancer drug, making it suitable for cancer therapy. Post formulation, we optimized our process by Reponse Surface Methodology (RSM) using Central Composite Design (CCD) and scaled up the formulation process in four stages with final scale-up process yielding 5 g of curcumin loaded nanoparticles within the laboratory setup. The nanoparticles formed after scale-up process were characterized for particle size, drug loading and encapsulation efficiency, surface morphology, in vitro release kinetics and pharmacokinetics. Stability analysis and gamma sterilization were also carried out.

Results

Results revealed that that process scale-up is being mastered for elaboration to 5 g level. The mean nanoparticle size of the scaled up batch was found to be 158.5 ± 9.8 nm and the drug loading was determined to be 10.32 ± 1.4%. The in vitro release study illustrated a slow sustained release corresponding to 75% drug over a period of 10 days. The pharmacokinetic profile of PLGA-CURC in rats following i.v. administration showed two compartmental model with the area under the curve (AUC_0-∞) being 6.139 mg/L h. Gamma sterilization showed no significant change in the particle size or drug loading of the nanoparticles. Stability analysis revealed long term physiochemical stability of the PLGA-CURC formulation.

Conclusions

A successful effort towards formulating, optimizing and scaling up PLGA-CURC by using Solid-Oil/Water emulsion technique was demonstrated. The process used CCD-RSM for optimization and further scaled up to produce 5 g of PLGA-CURC with almost similar physicochemical characteristics as that of the primary formulated batch.

Long-term stability, biocompatibility and oral delivery potential of risperidone-loaded solid lipid nanoparticles

A solid lipid nanoparticles (SLN) formulation to improve the oral delivery of risperidone (RISP), a poorly water-soluble drug, was designed and tested. Initially, lipid-RISP solubility was screened to select the best lipid for SLN preparation. Compritol(®)-based formulations were chosen and their long-term stability was assessed over two years of storage (at 25 °C and 4 °C) by means of particle size, polydispersity index (PI), zeta potential (ZP) and encapsulation efficiency (EE) measurements. SLN shape was observed by transmission electron microscopy (TEM) at the beginning and end of the study. The oxidative potential (OP) of the SLN was measured and their biocompatibility with Caco-2 cells was evaluated using the (4,5-dimethylthiazol-2-yl)2,5-dyphenyl-tetrazolium bromide (MTT) assay. In vitro drug release and transport studies were performed to predict the in vivo release profile and to evaluate the drug delivery potential of the SLN formulations, respectively. The RISP-loaded SLN systems were stable and had high EE and similar shape to the placebo formulations before and after storage. Classical Fickian diffusion was identified as the release mechanism for RISP from the SLN formulation. Biocompatibility and dose-dependent RISP transport across Caco-2 cells were observed for the prepared SLN formulations. The viability of SLN as formulations for oral delivery of poorly water-soluble drugs such as RISP was illustrated.

In vitro characterization and growth inhibition effect of nanostructured lipid carriers for controlled delivery of methotrexate

The present study describes the design and characterization of nanostructured lipid carriers (NLCs) for controlled delivery of methotrexate (MTX). A series of NLCs with or without MTX were prepared using different ratios of liquid-lipid to solid-lipid and type and concentration of surfactants. The effect of different formulation parameters on the physical properties of NLCs, entrapment efficiency of MTX and in vitro drug release was evaluated. In addition, the in vitro delivery and cytotoxicity of MTX-loaded NLCs against human prostate cancer DU-145 cells and ovarian human cancer A2780 cells were investigated. Drug loading capacity, particle size and surface charge of the prepared NLCs and the in vitro MTX release were affected by the formulation parameters. In vitro growth inhibition assay using DU-145 and A2780 cancer cell lines showed that drug-free NLCs maintained cell viability while MTX-loaded NLCs inhibited the growth of both cell lines. In addition, MTX-loaded NLCs showed superior inhibitory effect on cell growth over the free drug especially in A2780 cell lines and a higher cytotoxic effect on DU-145 at higher drug concentration. The results of the current study warrant further exploration for the use NLCs as a controlled delivery system for chemotherapeutic agents.

Optimizing flurbiprofen-loaded NLC by central composite factorial design for ocular delivery

The purpose of this study was to design and optimize a new topical delivery system for ocular administration of flurbiprofen (FB), based on lipid nanoparticles. These particles, called nanostructured lipid carriers (NLC), were composed of a fatty acid (stearic acid (SA)) as the solid lipid and a mixture of Miglyol(®) 812 and castor oil (CO) as the liquid lipids, prepared by the hot high pressure homogenization method. After selecting the critical variables influencing the physicochemical characteristics of the NLC (the liquid lipid (i.e. oil) concentration with respect to the total lipid (cOil/L (wt%)), the surfactant and the flurbiprofen concentration, on particle size, polydispersity index and encapsulation efficiency), a three-factor five-level central rotatable composite design was employed to plan and perform the experiments. Morphological examination, crystallinity and stability studies were also performed to accomplish the optimization study. The results showed that increasing cOil/L (wt%) was followed by an enhanced tendency to produce smaller particles, but the liquid to solid lipid proportion should not exceed 30 wt% due to destabilization problems. Therefore, a 70:30 ratio of SA to oil (miglyol + CO) was selected to develop an optimal NLC formulation. The smaller particles obtained when increasing surfactant concentration led to the selection of 3.2 wt% of Tween(®) 80 (non-ionic surfactant). The positive effect of the increase in FB concentration on the encapsulation efficiency (EE) and its total solubilization in the lipid matrix led to the selection of 0.25 wt% of FB in the formulation. The optimal NLC showed an appropriate average size for ophthalmic administration (228.3 nm) with a narrow size distribution (0.156), negatively charged surface (-33.3 mV) and high EE (∼90%). The in vitro experiments proved that sustained release FB was achieved using NLC as drug carriers. Optimal NLC formulation did not show toxicity on ocular tissues.

Design and ocular tolerance of flurbiprofen loaded ultrasound-engineered NLC

Packaging small drug molecules, such as non-steroidal anti-inflammatory drugs (NSAIDs) into nanoparticulate systems has been reported as a promising approach to improve the drug's bioavailability, biocompatibility and safety profiles. In the last 20 years, lipid nanoparticles (lipid dispersions) entered the nanoparticulate library as novel carrier systems due to their great potential as an alternative to other systems such as polymeric nanoparticles and liposomes for several administration routes. For ocular instillation nanoparticulate carriers are required to have a low mean particle size, with the lowest polydispersity as possible. The purpose of this work was to study the combined influence of 2-level, 4-factor variables on the formulation of flurbiprofen (FB), a lipophilic NSAID, in lipid carriers currently named as nanostructured lipid carriers (NLC). NLC were produced with stearic acid (SA) and castor oil (CO) stabilized by Tween® 80 (non-ionic surfactant) in aqueous dispersion. A 2(4) full factorial design based on 4 independent variables was used to plan the experiments, namely, the percentage of SA with regard to the total lipid, the FB concentration, the stabilizer concentration, and the storage conditions (i.e., storage temperature). The effects of these parameters on the mean particle size, polydispersity index (PI) and zeta potential (ZP) were investigated as dependent variables. The optimization process was achieved and the best formulation corresponded to the NLC formulation composed of 0.05 (wt%) FB, 1.6 (wt%) Tween® 80 and a 50:50 ratio of SA to CO, with an average diameter of 288 nm, PI 0.245 of and ZP of -29 mV. This factorial design study has proven to be a useful tool in optimizing FB-loaded NLC formulations. Stability of the optimized NLC was predicted using a TurbiScanLab® and the ocular tolerance was assessed in vitro and in vivo by the Eytex® and Draize test, respectively. The developed systems were shown physico-chemically stable with high tolerance for eye instillation.